Wastewater plants as unrecognized air polluters: extreme H₂S, CH₄, and industrial-linked NO₂ emissions in arid Jordan

Abstract

This study presents an analysis of air pollutant emissions from Jordan's Al-Baqa'a and As Samra Wastewater Treatment Plants (2018–2023). The analysis reveals the water–air quality nexus in arid urban environments. Through geospatial modelling and dispersion analysis, it is shown that biological treatment processes generate hydrogen sulfide (H₂S) concentrations of 182 ppb (17.7 times Jordan's standard). Interactions with nearby petroleum and pharmaceutical industries contribute 19–63% of ambient sulfur dioxide (SO₂) and nitrogen oxide (NO₂) loads. Methane (CH₄) is a primary biogas component and greenhouse gas emission component. Biogas composition averages 62±8% CH₄ by volume and contributes 14% of facility carbon footprints (1 230 t CO₂e/yr). Seasonal patterns exist: summer temperatures accelerate microbial conversion rates (Q₁₀ = 2.3) and produce NO₂ peaks of 181 ppb – 2.3 times the national limit. VOC measurements show benzene levels (2.1±0.8 ppb) exceed WHO cancer risk thresholds in 17% of samples near industrial zones. The methodology combines terrain modelling (30 m SRTM data) with atmospheric simulations (COD = 0.27, |FB| = 0.18) to quantify exposure disparities. Communities near WWTPs experience particulate matter concentrations 4.7 times higher than background areas. The findings inform three mitigation pathways: process optimization through extended sludge retention (15.3±1.2 days) reduces H₂S by 41%; chemical scrubbers achieve 89% SO₂ removal; IoT-enabled systems cut NO₂ peaks by 33%. This work establishes the role of wastewater infrastructure as part of urban air quality management. It provides solutions for Jordan's regulatory compliance and a framework for addressing the climate–pollution nexus in water-stressed regions.